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Imagining a successor to the Affordable Accuracy Monitor

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I’m currently doing Dennis Murphy’s Affordable Accuracy Monitor mod on an old pair of BS22s, and a thing that strikes me about them is the platonic ideal of a speaker mod. It’s not just that it takes a solid speaker and makes it great, it is that it does so with easily accessible parts, public knowledge and a base that, during its time, went on sale constantly. It meets people half way and isn’t going to break the bank. Like the Realistic Minimus 7 mods of old, they sold a million of these things, although Pioneer long since retired them.

This led me to an obvious question: what would today's Affordable Accuracy Monitor mod look like, and is it even possible? What is a plentiful speaker that is already quite good but suffers from a handful of weaknesses that a home hobbyist could fix? The Sehlin mod by @Mudjock is the best example since, although the Swans are a full kit. In the mic building world, the AKG Perception mod is another good example: a single capacitor tweaks a miscalculation about the tone of the capsule and gets it shockingly close to a u87.

Based on the current recommended passive speaker list a few options seem promising.
  • Dayton Audio MK402X
  • Polk Audio XT15
  • Polk Audio XT20
  • Kef Q150
  • Monoprice Monolith Encore B6
This is only from the list of recommended speakers. Other speakers, like the lower end ELAC debut 2.0 or 3.0, may make for a more interesting platform and an appropriate one given Andrew Jones’ tenure.

Again this is just a thought experiment. I agree with the wisdom that money spent on mods is more often better spent just buying better speakers, particularly when you factor in new drivers and crossover tweaks. You shouldn’t mod a speaker just for the sake of doing it. I am also aware that speaker design is complex, very difficult, and that hobbyists are going up against professionals. But compromises are often made at scale to get a good enough result. So, is an equivalent to an Affordable Accuracy Monitor even possible today? And what would that mod even look like?
 
I’m currently doing Dennis Murphy’s Affordable Accuracy Monitor mod on an old pair of BS22s, and a thing that strikes me about them is the platonic ideal of a speaker mod. It’s not just that it takes a solid speaker and makes it great, it is that it does so with easily accessible parts, public knowledge and a base that, during its time, went on sale constantly. It meets people half way and isn’t going to break the bank. Like the Realistic Minimus 7 mods of old, they sold a million of these things, although Pioneer long since retired them.

This led me to an obvious question: what would today's Affordable Accuracy Monitor mod look like, and is it even possible? What is a plentiful speaker that is already quite good but suffers from a handful of weaknesses that a home hobbyist could fix? The Sehlin mod by @Mudjock is the best example since, although the Swans are a full kit. In the mic building world, the AKG Perception mod is another good example: a single capacitor tweaks a miscalculation about the tone of the capsule and gets it shockingly close to a u87.

Based on the current recommended passive speaker list a few options seem promising.
  • Dayton Audio MK402X
  • Polk Audio XT15
  • Polk Audio XT20
  • Kef Q150
  • Monoprice Monolith Encore B6
This is only from the list of recommended speakers. Other speakers, like the lower end ELAC debut 2.0 or 3.0, may make for a more interesting platform and an appropriate one given Andrew Jones’ tenure.

Again this is just a thought experiment. I agree with the wisdom that money spent on mods is more often better spent just buying better speakers, particularly when you factor in new drivers and crossover tweaks. You shouldn’t mod a speaker just for the sake of doing it. I am also aware that speaker design is complex, very difficult, and that hobbyists are going up against professionals. But compromises are often made at scale to get a good enough result. So, is an equivalent to an Affordable Accuracy Monitor even possible today? And what would that mod even look like?
Perhaps it would make more sense to find cheap manufacturers for the milled fronts or housing kits on the individual continents and to use, for example, the very well developed and tested Mechano23 loudspeaker from @XMechanik.
Assuming that is OK for @XMechanik.

The housing quality with 18-22mm multiplex plywood or MDF should be better than anything you can buy in this price range and it is easy to build with a prefabricated front.
Small 2-way speakers with linear on-axis and power response characteristics (Scan Speak and SB Acoustics drivers). H&V off-axis measurements included
Mechano23 Open-source DIY Speaker Review
 
Perhaps it would make more sense to find cheap manufacturers for the milled fronts or housing kits on the individual continents and to use, for example, the very well developed and tested Mechano23 loudspeaker from @XMechanik.
Assuming that is OK for @XMechanik.

The housing quality with 18-22mm multiplex plywood or MDF should be better than anything you can buy in this price range and it is easy to build with a prefabricated front.
Small 2-way speakers with linear on-axis and power response characteristics (Scan Speak and SB Acoustics drivers). H&V off-axis measurements included
Mechano23 Open-source DIY Speaker Review
Somehow I had missed the @XMechanik mod and the subsequent review of it entirely, great stuff. I like the custom PCB. And I agree that making a quick and easy enclosure seems like a great idea.

I will say though that is slightly different from the original premise: what made the AAM great was repurposing an already plentiful speaker. I think it’s worth mentioning this DIYAudio thread tearing down the KEF Q150s. Figuring out the specific weakness in that speaker would be fantastic, I believe Erin’s measurements said there is cabinet resonance that is pretty nasty, and the crossover looks fairly simple and cheap.
 
I have pondered a comparable effort to the AAM, but struggle with the value proposition for the following reasons:
  1. Finding a suitable candidate and building consensus around it. If it is a current model, why should the supplier of a marginal product deserve a sales boost from a “free” redesign?
  2. Is it fair to small startups to elevate a redesign candidate to potentially compete with their work?
  3. Seems insulting to original designer to pick apart their work like GR’s upgrades kits do.
  4. ASR cannot do a commercial design or redesign project without looking biased towards the company.
Given this, my sense is that the AAM concept fit a point in time and, shy of a major designer endorsing as Dennis did, it has some high hurdles to prove its value.
 
From what I have seen and experienced, successful mods are a product of a specific opportunity. In the case of my HIVI DIY-3.1A mod, there was a very good set of drivers and an obviously flawed frequency response curve that I found could be addressed with crossover changes that didn't make the kit particularly more difficult to assemble for a typical customer. In the AAR case, the design was fundamentally pretty good, but hamstrung by the need to hit a very low retail price. If I recall correctly, Dennis had to swap out the tweeter in that case. Many years ago, Dennis had a mod for the Parts Express BR-1 kit. In that case, the low cost woofer delivered great bass, but was lacking in midrange output and quality.

I personally think if you can take a flawed budget product with some strengths to exploit and add some cost and/or effort to create something suitable for a more discerning listener who still wants to stick to a budget, a modification project can still have merit. I have to admit I was somewhat surprised how many people bothered to do my mods - even before the positive ASR review.
 
I have pondered a comparable effort to the AAM, but struggle with the value proposition for the following reasons:
  1. Finding a suitable candidate and building consensus around it. If it is a current model, why should the supplier of a marginal product deserve a sales boost from a “free” redesign?
  2. Is it fair to small startups to elevate a redesign candidate to potentially compete with their work?
  3. Seems insulting to original designer to pick apart their work like GR’s upgrades kits do.
  4. ASR cannot do a commercial design or redesign project without looking biased towards the company.
Given this, my sense is that the AAM concept fit a point in time and, shy of a major designer endorsing as Dennis did, it has some high hurdles to prove its value.
Fair points and I agree with the potential political implications of ASR officially taking some kind of stance on a mod.

I think it’s worth considering how many people would actually do a mod. If the product line is large enough, then probably not enough to matter when it comes to the overall sales numbers of the original company. What percentage of BS22s were converted to a AAM relative to just being sold at Best Buy? Not zero but relatively speaking not a lot.

I also do agree that there is a degree of hubris in doing what GR Research does, but I think a lot of that comes down to the mods being sold. Thats always been the thing I’ve hated about upgrade kits vs. tinkering. One of those can quickly become snake oil and the other is crowd sourced forum research and those are two different things. I’m not saying it can’t be done, but there’s a tone to it that rubs me the wrong way and often makes it a questionable value proposition.

As for insulting the original designer, I don't necessarily know if I agree. Speakers produced for a mass market are a series of economic compromises that a hobbyist is not beholden to. I don’t think it’s insulting to want to put a little more love into a product made for the largest possible profit margin. I think everyone knows how these things work, and if anything that’s a kind of flattery. I spend a lot of time on Marketplace and Craigslist and to me there is also something to giving a mass market commercial product new life. Done well, these things can be done with love, but I also powder coated my espresso machine for fun so I could be biased.

I’m willing to accept that the AAM was a time and place quirk. If anything a soup to nuts open source product is probably the future. But it’s always nice to explore what’s possible.
 
MK402X is not a good candidate, the driver quality is lacking. The other speakers on your initial list have decent drivers but the pricing is quite a bit higher and the stock crossovers are not that terrible, EQ can fix them.

A good candidate would be something like the Klipsch KD-51M aka Jamo S803. $120-150 per pair, desperately needs a new woofer crossover and probably a port plug for the resonances.

 
Wouldn’t the Numi BS5 or the Sony SS-CS5 also be in that range?
Neumi BS5 seems to have lower woofer sensitivity and fewer flaws. Ports plugs + 2-3 bands of EQ and it is golden.

Sony SS-CS5 just needs the super-tweeter disconnected and EQ to pull down the 1000Hz peak. The dips at 3000 and 7000Hz are probably diffraction and not fixable with a new crossover.
 
The problem is that the Pioneer SP-BS22-LR comes from a time when such speakers were sold in large quantities as take-away items in electronics stores, discount stores, department stores and cheap hi-fi shops. Only with these very high production numbers was it possible to install high-quality output components such as the housing, bass-midrange speaker, crossover and terminal. The tweeter wasn't bad, but just couldn't keep up.

We're talking about a pair of speakers here that had an RRP of $/€ 120-150 and were sold for as little as $/€ 60.
The market (Bluetooth speakers of all sizes) and the sales locations/markets have changed completely. One of many reasons why Pioneer and other manufacturers have run into such problems.

The high-quality MDF housing in particular is likely to have had a significant influence. Many people don't even realize how much more stable and less resonant the curved side walls are.

The acceptance or spread of a mod depends very much on the purchase price and the achievable performance.
At $/€ 300-400, acceptance and interest are likely to drop dramatically, partly because in this price range there is the Elac DBR-62 with similar performance (Spinorama) but deeper bass.
 
We're talking about a pair of speakers here that had an RRP of $/€ 120-150 and were sold for as little as $/€ 60.
The market (Bluetooth speakers of all sizes) and the sales locations/markets have changed completely. One of many reasons why Pioneer and other manufacturers have run into such problems.
are.
I do agree with this point a lot, the market has changed completely particularly when it comes to passives. You aren’t going to get big box stores carrying passive speakers the same way, sound bars kinda ate big parts of the market. I also think it’s worth factoring in a slight bump for inflation when calculating the original cost of the speakers and the mod. If a new mod were to exist, it would have to be different because the speaker world has changed.

That said I am curious about those Monoprice Monoliths. I also think it’s worth considering a mod that exists at a slightly higher price point, although I agree the math gets dicy there.
 
I do agree with this point a lot, the market has changed completely particularly when it comes to passives. You aren’t going to get big box stores carrying passive speakers the same way, sound bars kinda ate big parts of the market. I also think it’s worth factoring in a slight bump for inflation when calculating the original cost of the speakers and the mod. If a new mod were to exist, it would have to be different because the speaker world has changed.

That said I am curious about those Monoprice Monoliths. I also think it’s worth considering a mod that exists at a slightly higher price point, although I agree the math gets dicy there.
The Monolith Encore B6 is an interesting speaker, but outside the USA it is not available in many countries (Europe), or is far too expensive, e.g. € 600/pair.
At Monoprice, products also disappear from the range overnight.
Elac DBR 62 or Debut 2.0 B6.2 or B5.2 would also be interesting projects.
 
I see @Rick Sykora 's points, but I think a good mod idea won't step on toes unduly.

I don't think it's insulting to the original designer if the mod does something helpful to the speaker that doesn't scale well in mass production. I.e. something they would do in a more expensive speaker that they can't really do in a budget speaker.

I agree with @BoysRBackinTown that the DIY scene is de minimis compared to commercial sales and if I were a boutique speaker designer I wouldn't lose sleep over modders tweaking speakers.

I may be a 'man with a hammer' when it comes to 3D printing, but I think that's the route a mod should take in 2024.

Plenty of speakers out there today have pretty good drivers and overall design but have some issues at the crossover as well as a flat baffle.

A good mod would be a 3D printed baffle replacement with rounded edges and a waveguide - probably inevitably paired with a replacement crossover.

A lot of people have a 3D printer, or have a friend with one. It's not a process that's easy to scale in mass production. And there are a lot of speakers that could improve with a waveguide.

Print the baffle, fill it with plaster for density, mount the drivers, swap the crossover, glue the baffle to the cabinet, and there you go.

Of course, if we are talking about swapping in crossovers, we're probably talking kits that cost as much as the speaker. So maybe the whole thing doesn't make sense at all.
 
Would this one qualify?

 
Would this one qualify?

I forgot entirely about that one, I think a friend had some Truths I’d been meaning to mod. It’s in the right spirit but I’m imagining passives more than Actives. Those are noteworthy though and in the right spirit because those go Behringer has massive volume but also doesn’t thoroughly tune their speakers enough.
 
Yes. Shame it never got fully measured here.

 
To add to the thread: though it does not hit the same price point, I think it’s worth examining the KEF Q series for a few reasons.
  • The coaxial driver in this line is already very good and the star of the show. (here is the Q100 driver as measured by Erin contrasted with the LS50 Meta)
  • Basically every speaker in the line, including the Q3 Meta (according to Erin) seems to have the same issue with cabinet resonance.
  • The crossover (the crossover for the Q100/Q150 are here) looks comically simple and I bet it could be improved.
  • These things sold like hotcakes and are often in the secondhand market.
  • Mods for this already exist. I believe user @maty has posted about this both on DIYAudio as well as the ASR thread for the Q100. They mentioned using Tecsound SY70 or another viscoelastic material for the cabinet. I wonder how something like Sonic Barrtier, or even Dynamat or resonex would perform. The full Q100 thread has a lot from maty here, here, here and here. I would love to hear @maty chime in.
The cabinet resonance could theoretically be fixed using either dampening or by building a new cabinet. I would err on the side of dampening since at that point you’re basically making a whole new speaker (which user Jokerbre did). As for the crossover, this has been explored a bit by Jokerbre on the DIYAudio with the Q100. At the time the BOM came out to about 92 dollars for the crossover. There is a lot of daylight price-wise between KEF's Q series and the LS50 Meta/R3 Meta so an affordable upgrade like this has some potential for improving a speaker that is already plentiful in secondary markets. I do concede that it's in striking range of potentially better speakers at that point, but KEF isn't going to stop making these, so I think it's worthwhile to imagine potential fixes for an imperfect speaker with a great driver that goes on sale pretty frequently.


KEF-Q100-crossover.png


Stock Q100 crossover via Maty.

KEF-Q150-crossover.png

Stock Q150 Crossover via Maty.

SKRETNICA.png

The redesigned Q100 crossover via Jokerbre.

0.jpg

Measured on-axis frequency response via Jokerbre (not Klippel NFS but still looks promising).

IMG_5752.jpg

The finished DIY Q100s.
 
I don't find many of the "objections" relevant. If I buy a car (or anything else) that is not as good as it can be and I want to modify it, I don't care what it does to sales, the success of startups, or insults the designer of the car. Why would I care about those things when it comes to speakers?

I think the challenge, as already stated, is finding a suitable candidate given the market has changed some since the AAM days. Two things I'd look for (1) is there a reasonably good speaker that just doesn't measure well and could use a crossover mod; or (2) Is there a speaker that has a quality cabinet and either a good woofer/tweeter, but a not-so-good tweeter/woofer. Then upgrade the weak link and mod the xo.

Looking on Amazon, there are dozens of bookshelf speakers under $300. Maybe we should keep a running list of the potential candidates?
 
To add to the thread: though it does not hit the same price point, I think it’s worth examining the KEF Q series for a few reasons.
  • The coaxial driver in this line is already very good and the star of the show. (here is the Q100 driver as measured by Erin contrasted with the LS50 Meta)
  • Basically every speaker in the line, including the Q3 Meta (according to Erin) seems to have the same issue with cabinet resonance.
  • The crossover (the crossover for the Q100/Q150 are here) looks comically simple and I bet it could be improved.
  • These things sold like hotcakes and are often in the secondhand market.
  • Mods for this already exist. I believe user @maty has posted about this both on DIYAudio as well as the ASR thread for the Q100. They mentioned using Tecsound SY70 or another viscoelastic material for the cabinet. I wonder how something like Sonic Barrtier, or even Dynamat or resonex would perform. The full Q100 thread has a lot from maty here, here, here and here. I would love to hear @maty chime in.
The cabinet resonance could theoretically be fixed using either dampening or by building a new cabinet. I would err on the side of dampening since at that point you’re basically making a whole new speaker (which user Jokerbre did). As for the crossover, this has been explored a bit by Jokerbre on the DIYAudio with the Q100. At the time the BOM came out to about 92 dollars for the crossover. There is a lot of daylight price-wise between KEF's Q series and the LS50 Meta/R3 Meta so an affordable upgrade like this has some potential for improving a speaker that is already plentiful in secondary markets. I do concede that it's in striking range of potentially better speakers at that point, but KEF isn't going to stop making these, so I think it's worthwhile to imagine potential fixes for an imperfect speaker with a great driver that goes on sale pretty frequently.


View attachment 418405

Stock Q100 crossover via Maty.

View attachment 418406
Stock Q150 Crossover via Maty.

View attachment 418403
The redesigned Q100 crossover via Jokerbre.

View attachment 418407
Measured on-axis frequency response via Jokerbre (not Klippel NFS but still looks promising).

View attachment 418404
The finished DIY Q100s.
I think it makes sense, and we could even offer a 3D printable baffle that curves like the LS50. (yep, man with a hammer). But I would bet some of the ripples in the upper frequencies could be dealt with by rounding stuff off more.

As a matter of fact, no reason the whole cabinet couldn't be 3D printed (if filled with something solid.) You can really get creative in terms of eliminating internal standing waves and resonances if you have no constraints on the shape.

e: I just saw in the thread, the cost of the crossover is estimated at $92... not sure if that's one or both channels, but it does illustrate the value-for-dollar trap in DIY. I think a kit-oriented project should aim to minimize the cost and complexity of the crossover, so I'd be curious as to how close the response could be at (say) $20 in components per channel.
 
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Looking on Amazon, there are dozens of bookshelf speakers under $300. Maybe we should keep a running list of the potential candidates?
I can’t edit the initial post but this seems like a good idea. Maybe a google doc?
 
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